Whilst it is known that copper coolers have been constructed with steel attachments which can subsequently be welded to the furnace shell or steel elements mounted thereon, these coolers cannot move to allow for expansion and contraction of the furnace shell or refractories. Likewise it is known to use coolers with flanges which are bolted to the furnace shell or steel elements mounted thereon, in such a manner as to allow the coolers to move slightly to accommodate relative movement between the shell of the furnace and the refractories in which the coolers are set. Whilst the coolers which can be attached to the furnace by welding have the advantage of ensuring gas tightness and add to the strength of the furnace additional cost and complication of the refractory lining is necessary to avoid the relative movement between the shell and the refractories due to expansion and contraction.